/prog/ challenge

Write a macro that, given a term of code, transforms all the calls to the function FOO in that term, and only those calls, into calls to function BAR with the same arguments.
Language: Common Lisp or Scheme.

>>73
(list 'foo 7)
>'(foo 7)
It's only a function call when you tell lisp to evaluate it. Since that hasn't happened, it's just a list.

Is '(7 7) a function call to the number 7?